perf(streaming): cursor publication across frame budgets

src/AcDream.App/Rendering/Wb/EnvCellLandblockPublication.cs

@@ -0,0 +1,45 @@
+using System.Numerics;
+
+namespace AcDream.App.Rendering.Wb;
+
+/// <summary>
+/// Narrow update-thread publication seam used by streaming. Preparation builds
+/// one private shell at a time; commit publishes the completed immutable
+/// landblock snapshot with one owner dictionary replacement.
+/// </summary>
+public interface IEnvCellLandblockPublisher
+{
+    EnvCellLandblockPublication PreparePublication(
+        EnvCellLandblockBuild build);
+
+    bool AdvancePreparationOne(EnvCellLandblockPublication publication);
+
+    void CommitPublication(EnvCellLandblockPublication publication);
+}
+
+public sealed class EnvCellLandblockPublication
+{
+    internal EnvCellLandblockPublication(
+        object owner,
+        EnvCellLandblockBuild build)
+    {
+        Owner = owner;
+        Build = build;
+        Replacement = new EnvCellLandblock
+        {
+            GridX = (int)((build.LandblockId >> 24) & 0xFFu),
+            GridY = (int)((build.LandblockId >> 16) & 0xFFu),
+        };
+        TotalBounds = new WbBoundingBox(
+            new Vector3(float.MaxValue),
+            new Vector3(float.MinValue));
+    }
+
+    internal object Owner { get; }
+    internal EnvCellLandblockBuild Build { get; }
+    internal EnvCellLandblock Replacement { get; }
+    internal WbBoundingBox TotalBounds { get; set; }
+    internal int ShellCursor { get; set; }
+    internal bool PreparationCommitted { get; set; }
+    internal bool PublicationCommitted { get; set; }
+}